The invention relates to a device for applying a threadlike implant with a pressure-generating, fluid-containing means that is connected with a casing accommodating the thread to be implanted, wherein the casing empties into a channel. The thread to be applied is introduced into the distal end of the channel. The pressure exerted on the fluid by the pressure-generating means enables transport of the thread to be implanted and located inside the casing through the distal opening of the channel, where the thread is discharged to the outside, or into a tissue or hollowed out body. Since the arrangement discharges the implant in threadlike form and through the channel, there is a potential application for operative microscopy.
Devices for applying a threadlike implant were already disclosed in WO 96 04954. A stream of fluid is generated in this channel, which transports the thread to be implanted through the channel. The fluid is then discharged along with the thread through the distal opening of the channel.
The object of the invention is to provide a device that can be used to apply a ball-shaped implant into a tissue or hollowed-out body, wherein the fluid necessary for transporting the thread remains in the device. The object is achieved according to the characterizing clause of claim 1.
The present invention makes it possible to inject the thread to be implanted against higher resistances. Since more force can be exerted on the thread with the device according to the invention in comparison to the devices in WO 96/04954, less flexible threads can also be implanted. In addition, the device according to the invention enables a minimally invasive implantation of threadlike implant materials without simultaneously discharging a fluid into the body. If threadlike implant materials and a fluid must be implanted together for certain medical applications, this can take place via two separate channels. As opposed to the devices described in prior art, the advantage to this is that implant material and fluid can be metered in separately and independently of each other. Likewise, the implanted thread volume can be precisely controlled and metered, because the volume forced out by the pressure-generating means corresponds to the implanted thread volume.
The implant applied with the device according to the invention is characterized by a thread ball in the form of a three-dimensional, open-pored structure. This thread ball is incorporated at a desired spot into the tissue or another point of the body to be treated via a small puncture or a hole in the body in operative microscopy, and in any amount. The thread ball is formed when the thread to be applied encounters a resistance in the tissue after exiting from the distal end of the channel, so that the ensuing thread sections are bent and finally stacked to form the desired thread ball. By moving the distal channel end while implanting a thread, the form of the implant can be varied within a wide framework and fixed intraoperatively. This yields a wide range of potential applications. The pore size and structural properties of the implant can be varied, for example via the diameter of the thread or by modifying the material properties of the thread, in particular bending strength, and can be set pursuant to the clinical requirements. The thread can be a carrier of biologically active substances, and is particularly suited for the controlled administration of drugs or induction of body tissue.
The device according to the invention is used, for example, during the treatment of urinary incontinence, for which a thread ball is injected into the tissue below the neck of the bladder to lift it. In addition, as described in WO 96/04954, it is used in the treatment of bone defects and plastic surgery in the form of tissue-inducing threads, which induce the generation of new bony, cartilage or connective tissue through the release of growth factors. In addition, the device according to this invention is used for the treatment of fistulas, aneurisms and therapeutic embolisation of blood vessels. Another important application is use as axe2x80x9cdrug delivery systemxe2x80x9d, for example through the local administration of cytostatics for cancer treatment, or the release of antibiotics for the treatment of infections. Another example involves cell transplantation, in which the threads are implanted with incorporated cells, e.g., Langerhan""s cells, using the device according to the invention.
The examples of the device according to the invention enumerated here constitute only a limited selection of various applications.
The device according to the invention is characterized by an opening in the area of the distal end of the mentioned channel. In terms of diameter or cross-sectional surface, this opening essentially corresponds to the threadlike implant material, which can also be a thread with non-circular cross section. The threadlike implant material is shifted through the opening via a pressure difference, during which no fluid stream is moved, as opposed to the design known from WO 96 04954. The fluid is only used to hydraulically convey the hydrostatic pressure built up by the pressure-generating means to the thread, which as a result gets pressed out of the distal opening of the channel of the device. As opposed to devices known from prior art, the device according to the invention does not envisage any fluid exiting from the opening along with the thread.
A non-compressible substance, e.g., water or oil, is suitable as a fluid to be used according to this invention, since the discharge of the thread into the tissue can be better monitored. For example, if the necessary pressure is applied via a piston pump-like system, a high pressure can be applied with vary little piston travel in the case of incompressible fluids, and the amount of implanted material corresponds to the displaced volume in the piston. In addition, the advantage to incompressible fluids is that the pressure can be diminished very rapidly and without fluid expansion.
Suitable incompressible fluids according to the invention include water, aqueous solutions (e.g., saline solutions), oils such as Soya bean oil, castor oil or paraffin, liquids with various additives, which help the thread slide through the opening in the device according to the invention, while compressible media include gases, such as nitrogen.
Another advantage to the invention lies in the fact that, in addition to threads with a high bending strength, use can also be made of very readily soft and flexible threads, e.g., rubbery threads, which more readily result in the desired irregular, spongy ball structures that are better suited for most applications in medicine than regular structures. However, regular structures can be an advantage for various applications.
Threadlike implant materials can include structures that exhibit a long length in comparison to the diameter, and which have a bending strength low enough that they can be shaped into ball-like structures during implantation. These structures can exhibit circular or differently shaped cross sections, or be monofilaments or multifilaments. It is important that the threadlike materials seal the distal narrowing of the channel in such a way that essentially no fluid can get out of the device. The distal narrowing can be shaped to reflect the thread cross sections, first to ensure a good seal, and second to simultaneously achieve passage of the thread through the narrowing with as little friction as possible.
In special cases, it is also conceivable to use threads with a higher bending strength, which cannot form any ball structures inside the body, e.g., to linearly advance a thread in the tissue using the device according to the invention, or to apply ordered structures, e.g., in the form of flat spiral springs.
Suitable materials for the threadlike implant include. synthetic polymers, such as silicone elastomers, polyhydroxymethacrylate (PHEMA) and hydrogels consisting of PHEMA, polyurethane, Dacron, polyesters such as polylactides or polyglycolides and polyorthoesters. Suitable bipolymers include collagen, gelatins, hyaluronic acid, chitosane and alginate. In addition, use can be made of composite materials such as monofilaments with reinforced threads comprised of glass threads, polymer threads or ceramic threads, as well as monofilaments mechanically reinforced by one or more long threads or a multifilament, monofilaments with incorporated particles, monofilaments comprised of various materials (resorbable or non-resorbable), e.g. with laminated structure, porous monofilaments, monofilaments that swell inside the body (quellable PHEMA or other hydrogels), monofilaments with X-ray contrast (also via incorporation of particles or threads or threads with X-ray contrast).
Injecting threads via the procedures known from prior art can under certain conditions be difficult if space for the implant in the tissue must be created during injection, e.g., as is the case in so-calledxe2x80x9ctissue bulkingxe2x80x9d. The force that must be exerted on the threads in this case to deposit them into the surrounding tissue is relatively high. According to the procedure described in WO 96/04954, the thread often becomes blocked during the implantation process, since a relatively low force is applied to advance the thread against the resistance of the tissue in the channel. The thread is advanced via the fluid used in WO 96/04954, which can be introduced with a corresponding pressure. The force on the thread can only cause the hollow space created by the fluid to be filled out by the thread material. Therefore, the structure of the implant will be very loose, and only contract or compact as the fluid is resorbed or siphoned off. The implant must be a specific size in the aforementioned xe2x80x9ctissue bulkingxe2x80x9d. Often, space for the implant cannot be created by overstretching, so that the desired volume can be reached later. In addition, it would likely be very difficult to meter the necessary thread amount, i.e., the implant volume, under these conditions.
Therefore, another advantage to the present procedure lies in the fact that the thread can be pressed directly into the tissue, and at most only a slight reduction in implant volume can be expected from changing the ball structure. In addition, it is possible to use soft threads with a higher bending strength in comparison to WO 96/04954, which cannot be applied with the device described in WO 96/04954.
Depending on clinical application, it may make sense to apply one or more threads with predetermined length, or to terminate application after a sufficient amount of threadlike implant material has been implanted. In the former case, the sudden exit of pressurized fluid after ejection of the proximal thread end is prevented by sealing the distal opening, or using a check valve between the pressure-generating means and casing. In the latter case, the thread is cut near the distal end of the channel or more proximally after the application of enough implant material. The distal part of the cut thread can then be completely ejected from the device before the channel is retracted from the treated body.